Definition of terms relating to maintenance & equipment performance

IPSS
0. FOREWORD
INTER PLANT STANDARD - STEEL INDUSTRY
DEFINITION OF TERMS RELATING TO
MAINTENANCE & EQUIPMENT
PERFORMANCE (First Revision)
Corresponding IS does not exist
IPSS : 3-02-006-07
Formerly:
IPSS:3-02-006-00
0.1 This Inter Plant Standard has been prepared by the Standards Committee
on Operation & Maintenance, IPSS 3:2 with the active participation of major
steel plants and was adopted in March 2007.
0.2 With the growing emphasis on adoption of quality system as per ISO 9000
series of standards, IPSS 3:2 has felt the necessity for having terms relating
to maintenance & equipment performance properly defined to avoid any
ambiguity of meaning and hence this standard.
0.3 These definitions are generally relevant to SAIL plants & units.
0.4 As per practice, Standard was reviewed and updated.
1. SCOPE
1.1 This standard covers definitions of terms relating to maintenance &
equipment performance.
2. DEFINITIONS
2.1 ASSEMBLY - An assembly is an orderly combination of individual
parts/sub-assemblies, which can perform desired function.
2.2 ASSET - An asset is Capital Item, which can independently by itself
produce goods or render services. An asset is not a spare item and can
render its service anywhere without reference to particular equipment.
2.3 ATTACHMENT & ACCESSORIES - An attachment or an accessory does
not necessarily form a spare part of equipment but enhances the
performances of the equipment when these are added on.
2.4 AVAILABLE HOURS- Installed calendar hours minus planned repair hours.
2.5 BREAKDOWN - Any unplanned stoppage of equipment/mechanism due to
damage to the equipment or system resulting in its inability to perform its
function.
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IPSS:3-02-006-07
2.6 BREAKDOWN MAINTENANCE - The maintenance carried out on an
equipment when it has already failed to perform its intended or desired
function.
2.7 COMPLETE UNIT - A complete unit is an equipment which can produce
goods or render service but can be used a spare part of larger installations
(pumps, compressors, motors, generators, cylinders, transformers etc.)
2.8 CONSUMABLE - A consumable is an item which is required for the
production process but does not form part of the end product.
2.9 CONDITION BASED MAINTENANCE SYSTEM - In this technique, the
maintenance is carried out depending on actual condition of equipment to
avoid failures. The condition of equipment is assessed and predicted after
checking by the application of any one or combination of following methods:
a) Use of basic human senses
b) Use of conventional primary instrument
c) Application of sophisticated tools
d) Through product quality
2.10 CAPITAL REPAIR - These are normally carried out once in a year or at
higher interval to bring back the equipment / unit to normal. The repair cost,
and cost of spares are capitalized.
2.11 CHECKING - Checking is a short time activity to find out and assess the
condition of equipment either with the help of human senses or aided with
small tools and is carried out on equipment either in running condition or
idle condition.
2.12 DESIGN OUT MAINTENANCE - When the failure of the same nature is
taking place again and again and no method of maintenance is able to
prevent failures, the equipment must be redesigned and it is known as
design out/re-design maintenance.
2.13 DELAY - Any unplanned stoppage of equipments or system affecting
production is considered as delay.
2.14 DESIGN DEFICIENCY - If the equipments/sub-assembly fails quite
frequently and is unable to perform under normal working condition, it is
considered to have design deficiency.
The lack of accessibility of the part of assembly for repairs, use of substandard
material, low factor of safety in original design, ignorance of
design aspects and regular failure are some of the reasons for design
deficiency.
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IPSS:3-02-006-07
2.15 FAILURE - Inability of an item or component to meet specified/intended
function, when the performance of unit goes below the expected norms.
2.16 INTERRUPTION - Interruption is a forced stoppage of otherwise smoothly
running system/production unit and is normally of short duration.
2.17 INSPECTION - Inspection is an activity where the machine part or the
equipment is examined closely and assessed for defects or deficiencies. It
can be short term or long term. Checking falls under short term inspection.
Long term inspection involves opening up the equipment and measuring
various parameters.
2.18 INSTALLED CALENDAR HOUR (ICH) - The no. of units multiplied by 24
hours in a day are installed calendar hour for the day and similarly for
month & year.
2.19 JIGS & FIXTURES - A jigs is an enabling attachment for a machining
operation which locates the points on work piece correctly and guides
the tool to perform the machining operation. It restricts the degrees of
freedom of an operating tool and work piece.
A fixture is an enabling attachment which locates the reference point on a
workpiece and limits its degree of freedom.
2.20 LIFE CYCLE TIME – This is the total period from commissioning of an
equipment till it has given its full functional life.
2.21 MAINTENANCE – Any action taken to keep/restore equipment or system in
a condition to perform its intended or desired function is termed as
Maintenance.
2.22 MAJOR REPAIR – This is defined where the duration exceeds 3 shifts but
less than 6 shifts and is not a capital repair.
2.23 MAINTENANCE DELAY – Any unplanned stoppage of equipments or
system affecting production due to the failure of the equipment, system is
mechanical delay. If it is a mechanical failure it is treated as maintenance
delay and if failure is electrical it is considered as electrical delay.
2.24 OPERATION DELAY – Operation delay is the delay due to Operational
agency affecting production and includes delays are non-availability of input
materials, stoppages of upstream facilities.
2.25 PLANNED MAINTENANCE/SCHEDULED MAINTENANCE – The
maintenance activities carried out with fore thought and control where all
aspects of jobs are considered so that maintenance information, planning,
special tools & tackles and safety of the job are taken care of, feedback of
the action taken and history records forms an integral and essential part of
planned maintenance.
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2.26 RUNNING MAINTENANCE – It is a form of preventive maintenance carried
out while the plant or equipment is continuing to perform its function. It
involves activities such as inspection, tightening the bolts, cleaning,
adjusting and lubrication. This can also be termed as “servicing”.
2.27 REVAMPING - Revamping is an activity of capital repair nature wherein
complete assemblies & sub-assemblies of an equipment are not only
changed but also new accessories and attachments are added to improve
performance of the equipment.
2.28 REBUILDING - Rebuilding as applied to steel industry generally refers to
Rebuilding of Coke Oven Batteries. This involves complete dismantling &
demolishing of the Oven structures above foundation and rebuilding of
entire new battery with its civil, structural and refractory works.
2.29 RELINING - It applies to relining of the Blast Furnaces, Hot Metal Mixer,
Open Hearth & Twin Hearth Furnaces, LD Converters, Soaking Pits and
Ladles. Relining involves complete dismantling of old worn out refractory
lining and putting new lining in its place.
2.30 RELIABILITY CENTRAL MAINTENANCE (RCM) - RCM is an integrated
maintenance strategy which determines maintenance requirement of each
item of equipments in its operating context. It recognizes that all the
possible approach to maintenance have part to play in modern
maintenance system. By taking consequences of failure into consideration it
helps in selecting the most appropriate maintenance strategy for any given
situation.
2.31 SUB-ASSEMBLY - A Sub-assembly is an orderly combination of individual
parts which can be used as replacement as a unit.
2.32 SHUTDOWN MAINTENANCE - It is often both preventive and corrective
work which is normally implemented when plant or equipment is taken out
of service specifically for maintenance.
2.33 SPARES - A spare of an equipment is a single part or sub-assembly
subjected to wear and can be replaced by another identical single part or
sub-assembly which restores the equipment's normal function. A spare is a
revenue item. A spare by itself can not serve any useful function.
2.34 TIME BASED MAINTENANCE - Replacement or repair at a fixed time
interval before failure is known is time based maintenance.
2.35 TOTAL DELAY - Total delay is sum of all delays due to various agencies
like operation, maintenance and services.
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MAINTENANCE INDICES
IPSS:3-02-006-07
2.38A GROSS EQUIPMENT AVAILABILITY
Installed Calendar Hours - Planned Repair Hours
________________________________________ x 100
Installed Calendar Hours
2.38B NET EQUIPMENT AVAILABILITY
ICH - (Planned + Unplanned Repairs in Hours)
________________________________________ x 100
Installed Calendar Hours (ICH)
2.39 EQUIPMENT UTILIZATION
ICH - (Planned Repairs + Total Delays)
________________________________________ x 100
Installed Calendar Hours
2.40 INSPECTION INDEX
No. of Inspections carried out
______________________________ x 100
No. of inspections planned
2.41 JOB FULFILLMENT
No. of jobs fulfilled
____________________ x 100
No. of jobs planned
2.42 CAPITAL REPAIR FULFILLMENT EFFECTIVENESS
No. of jobs actually done Job days planned
_________________________ x __________________
No. of jobs planned Job days actual
2.43 EMERGENCY WORK RATIO
Man hours spent on unplanned maintenance
____________________________________
Man hours spent on total maintenance jobs
2.44 EQUIPMENT FAILURE FREQUENCY
No. of occurrences of maintenance delays
______________________________________ x 100
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Installed Calendar Hours
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2.45 EQUIPMENT FAILURE INTENSITY
Maintenance delays in hours
_________________________ x 100
Installed Calendar Hours
2.46 MEAN TIME BETWEEN FAILURES (MTBF) - It is the mean time between
the occurrence of consecutive faults or failures and is a measure of
functional reliability.
2.47 MEAN TIME TO FAILURE (MTTF) - It is the average time from conclusion
of work to rectify a fault until the next fault occurs. It is also a measure of
functional reliability.
2.48 MEAN TIME TO REPAIR (MTTR) - It is the mean time to repair and is a
measure of equipment maintainability.
2.49 MAINTENANCE COST
Elements:
1. Spares consumption (purchase + in-house manufactured)
2. Labour Cost (Department + Contractual)
3. Cost of consumables & stores
4. Cost of services
_______________
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